function Map (el){
    //保存地图对象
    this.el = el
    //记录地图属性   
    this.width = 800
    this.height = 400

}
Map.prototype.create = function () {
    this.el.style.width = this.width + 'px'         //设置地图宽
    this.el.style.height = this.height + 'px'       //设置地图高
    this.el.style.background = 'url(./bg.png)'      //设置地图背景
    this.el.style.border = '15px solid red'         //设置地图边框
    this.el.style.position = 'relative'
}